Stephen Himson, Postgraduate Researcher

Are invasive species ('neobiota') a biostratigraphical and biological marker of the Anthropocene?

Contact DetailsStephen Himson

Project Overview

Humans modify the biosphere at an accelerating rate, directing evolution of species and ecosystems, trans-locating organisms across the globe, appropriating huge energy resources, and increasing biological interaction with technology. It can be argued that these changes are comparable in scale to those of deep time evolutionary transitions, with possible near-future trajectories that include mass extinction. These changes are part of a greater pattern of human modification to the atmosphere, hydrosphere and landscape that has left a distinctive geological signal of the Anthropocene.

In some places recent changes to biota are profound. The San Francisco Bay area is a clear example, being possibly the most biologically invaded aquatic ecosystem in the world. It is thus a prime setting to evaluate the degree of human impact on the biosphere and its potential biostratigraphical signal. In a seminal study by Cohen et al. (1998), some 234 neobiotic ‘invasive’ species were recognised in the Bay. They noted an accelerating trend of invasion over ca. 150 years, with about half the invasions occurring since 1960. More recently, studies of shallow sub-tidal sediments in the Bay have identified communities that are numerically dominated by invasive species. The presence of so many neobiota in San Francisco Bay, together with an established chronology of invasion, provides a means to assess the potential biostratigraphical expression of these changes over a timescale of 2 centuries.

Changes in San Francisco Bay are mirrored in Old World (e.g. Britain), and remote island (Hawaii) biological signatures. All these areas have a complex mosaic of human-influenced stratigraphic successions. But importantly, they share species that suggest inter-continental biostratigraphical ties can be established. Collectively these regions can be used to examine the global pattern of Anthropocene biotic change, and to assess the biostratigraphical pattern of the neobiota in the rock record across the world. They also comprise successions across a range of climate zones including tropical, warm temperate and cold temperate.

Research Theme

Evolution and Past Environments

Research Questions

  1. What is the biostratigraphical signature of human activity?
  2. How do invasive species impact ecosystems?
  3. Is there a globally correlatable signature of anthropogenic activity in the mid-20th century that can be recognised through biostratigraphy?
  4. Is the Anthropocene signal global, even in remote island successions such as Hawaii?


Williams, M., Zalasiewicz, J., Himson, S., Summerhayes, C., Barnosky, A., Leinfelder, R. 2018. The palaeontological record of the Anthropocene. Geology Today 34(5), pp. 188-193.

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